1. Field of the Invention
The present invention relates to a process for the production of a transition alumina having a larger specific surface area for applications of, for example, desiccants, absorbents, catalysts and catalyst supports.
2. Description of the Related Art
The transition alumina has been widely used for various applications such as the desiccants, the absorbents, the catalysts and the catalyst supports, and it is expected to be used for further applications.
From view points of increase of an absorbent capacity for water or an intended absorbed component and effective application of the catalysts, the transition alumina used for the above applications is required to have a larger specific surface area.
Conventionally known process for the production of the transition alumina includes a process as described in Japanese Patent Kokoku Publication No. 21319/1975 in which alumina hydroxide produced by the Bayer's process is thermally decomposed in an air flow at an elevated temperature, a process as described in Applied Catalysis, Vol. 24, pp. 25-35, 1986 in which an aluminum salt or an aluminate is hydrolyzed to produce an amorphous alumina gel and the resultant alumina gel is calcined and a process as described in Ceramics, Vol. 24, No. 11, pp. 1042-1047, 1989 in which an aluminum alkoxide is hydrolyzed and calcined. The transition alumina produced by the above processes has a specific surface area of not larger than 350 m.sup.2 /g.
Even a commercially available transition alumina having the largest specific surface area has a specific surface area of about 340 m.sup.2 /g as described in Table 11.25 of Chemical Society of Japan, Chemical Handbook-Applied Chemistry II (Materials), 3rd ed., Maruzen, Tokyo, p. 865.
On the other hand, a process for the production of the transition alumina in which an aluminum sulfate is thermally decomposed is known from, for example, Japanese Patent Kokoku Publication No. 16934/1967, Yogyo Kyokai Shi (J. Ceram. Ass. Jpn.), Vol. 77, No. 2, pp. 60-65, 1969 and Gendai-Kagaku-Koza 18, Inorganic Synthetic Chemistry II, Kyoritsu-Shuppan, Tokyo, p. 113.
Gendai-Kagaku-Koza 18, Inorganic Synthetic Chemistry II, p. 113 describes that the alumina produced by the process described therein comprising thermal decomposition at a temperature of about 900 .degree. C. has a specific surface area of about 170 m.sup.2 /g.